1. Field of the Invention
The present invention relates to a filter element utilized in an oil filter, air cleaner device, fuel filter, or the like.
2. Description of the Related Art
An automobile, for example, is equipped with a fuel filter which includes a filter element for the purpose of removing contaminants from fuel which is supplied to an engine.
As shown in FIG. 10, the filter element may uses flat filtering material 181 and corrugated filtering material 182. In fabricating this filter element, adhesive 2a is applied in narrow stripes along the longer direction (corrugating direction) to the corrugated filtering material 182 on the upper side (upstream or fuel inlet side) 71 and to the flat filtering material 181 on the lower side (downstream or fuel outlet side) 79, respectively. Following this, the flat filtering material 181 is overlaid with the corrugated filtering material 182, and these materials are then rolled into a spiral shape.
In the above-mentioned filter element, it is not necessary to align with care the flat filtering material 181 and the corrugated filtering material 182 when performing rolling. In addition, the corrugated filtering material 182 is in the configuration most easily formed when forming with a corrugated roller. Because of this, efficiency is good and productivity is good as well.
However, the ratio of the open area of the fuel inlet path 14 on the upper side 71 to the sealed area of the fuel outlet path 16 is 1:1, and the cross-sectional configuration of both is symmetrical. The inlet path 6 is desired to be large enough because the fuel 6 may include contaminants therein. However, because of the above configuration, the amount of fuel 6 entering into the inlet path 14 is restricted, and filter performance is inadequate.
The fuel filter of Japanese Patent Application Laid-open No. 126907/1990 (U.S. Pat. No. 5,002,666) has been proposed in this regard.
As shown in FIGS. 11 and 12, the above-mentioned fuel filter is provided midway in a fuel line 90, which supplies fuel 6. The fuel filter 9 comprises a filter case 91, a cover 92 installed atop the filter case 91, and a filter element 1 contained within the filter case 91.
Fuel 6 enters the fuel filter 9 via an inlet 920 formed in the center of the cover 92, is filtered by the filter element 1, and is supplied to the engine not illustrated via an outlet 930 formed in the center of the bottom of the filter case 91.
As shown in FIG. 13 further, the filter element 1 may be porous filter paper 10 which has been fabricated in a corrugated shape with alternate mountains and valleys and which is then rolled into a spiral shape to form a tubular configuration.
The corrugated filter paper 10 is bonded such that the respective valleys 131 and 151 and the respective mountains 139 and 159 of corrugated filtering materials 13 and 15 are facing each other. Alternating tubular inlet paths 14 and outlet paths 16 are formed between the mountains 139 and 159. As shown in FIG. 12, the lower side 79 of the inlet paths 14 is bonded with adhesive 2b.
In addition, as shown in FIG. 12 and FIGS. 14A and 14B, the upper side 71 of the outlet paths 16 is bonded with adhesive 2a.
The inlet paths 14 are open on the upper side 71 and closed on the lower side 79. Meanwhile, the outlet paths 16 which are adjacent to the inlet paths 14 are closed on the upper side 71, and the lower side 79 is open.
In this filter element 1, as shown in FIG. 12, fuel 6 flows into the inlet paths 14 from the upper side 71, and the fuel 6 passes through porous filter paper 10, passing from the inlet paths 14 to the outlet paths 16. At this time, contaminants mixed in with the fuel 6 are trapped on the filter paper 10 on the side of the inlet paths 14.
The above-mentioned fuel element 1 may also be utilized as any of various types of filters for air cleaners and the like in addition to use as a fuel filter for automobiles.
Next, in manufacturing the foregoing filter element, lengthy filtering material is first formed into a corrugated configuration to fabricate corrugated filtering materials 13 and 15, as shown in FIG. 13. Following this, adhesive 2a and 2b is applied in narrow stripes along the longer direction to the corrugated filtering material 13 on the upper side 71 and to the corrugated filtering material 15 on the lower side 79, respectively. Next, the corrugated filtering materials 13 and 15 are laid one atop the other such that the respective valleys 131 and 151 and mountains 139 and 159 of the corrugated filtering materials 13 and 15 face each other as shown in FIG. 14B, and filter paper 10 is obtained. Following this, the filter paper 10 is rolled along the direction of length into a spiral shape.
However, when rolling the foregoing roll filter paper 10, the adhesive 2a and 2b may protrude as shown in FIG. 14A, or the bonding of the adhesive may be imperfect. Because of this, the chance exists that the lower side 79 of the inlet paths 14 and the upper side 71 of the outlet paths 16 may not be perfectly closed.
In addition, when superposing the corrugated filtering material 13 and the corrugated filtering material 15, it is necessary to perform alignment with care so that the respective valleys 131 and 151 and the respective mountains 139 and 159 face each other, which poses problems in productivity for volume production.
In addition, if the tubes of the inlet paths 14 and outlet paths 16 are not bonded inter alia, an imperfect seal is obtained, and dust-filtration performance is diminished.